Battle of Rocroi

The Battle of Rocroi was a major battle of the Thirty Years' War and Franco-Spanish War which occurred on 19 May 1643. A French army under Louis II de Bourbon, Prince de Conde destroyed a Spanish army under Francisco de Melo as it invaded northern France, demonstrating the superiority of firepower against the Spanish tercio formation.

Background
In 1643, the Spanish had all the initiative along the Rhine, as France was led by the sickly Louis XIII of France, who died on 14 May. Many Imperials thought that France would not pose a threat as King Louis died, and that Spain should focus on the Netherlands, but the Spanish general Francisco de Melo was confident that he and his 28,000-strong army could defeat France in a decisive battle and force them to sue for peace. On 10 May 1643, his army crossed the French border, targeting the small but strategic fortress of Rocroi, held by 1,000 French troops. The 22-year-old Louis II de Bourbon, Prince de Conde and his 21,000-strong French army the marched towards the Spanish army as it besieged Rocroi. The Spanish were ready to assault Rocroi on 17 May, but, on 18 May, De Melo learned of Conde's approach.

Battle
On 18 May 1643, Conde led his men in a risky maneuver through a narrow pass, with De Melo learning of the French movement too late. The French crossed the defile and deployed, and this partially worked in Spain's favor, as the French would be unable to retreat easily. Some French cavalry launched an attack on the Spanish army without orders, inadvertently buying time for the rest of the French army to arrive. Unlike the Spanish infantry, who fought in tercios, the French deployed in lines. Conde decided to attack before the Spanish could be reinforced, and he sent part of his reserve to the forest to thwart a Spanish ambush. At 4:00 AM on 19 May 1643, the French artillery bombardment began, and he commanded his wings to advance an hour later. Another French cavalry attack on the Imperial flank failed, with Ernst von Isenburg capturing the French general De la Ferte. He then had his troops focus on the French infantry in the center, while the right flank of the Spanish center joined the attack, inflicting heavy losses on the first French line. By 6:00 AM, it was feared that the French had lost the battle, but, from 4:00 to 5:00 AM, the French reserves in the forest had destroyed a Spanish ambush force and attacked the Spanish left. The Spanish forces on the left were destroyed by a pincer movement, and more French ambush troops attacked Spanish reinforcements from three sides on their flank. The Spanish cavalry escaped while their infantry were massacred, and the French right flank attacked the Spanish tercios on the second and third lines of their left flank. The Spanish second and third line battalions were broken by the flank attack, and Von Isenburg failed to outflank the French line battalions, leading to his unit becoming outnumbered. He and the tercios fighting next to him had a vulnerable left flank, and the French cavalry reserve attacked him there. The Spanish vainly waited for reinforcements, and they were flanked and pushed back. By 8:00 AM, the second and third lines of the Spanish center had been destroyed, and Conde then attacked Von Isenburg from the rear and overwhelmed his troops. Paul-Bernard de Fontaine ordered his five remaining tercios and the small remaining groups of Spanish survivors to form squares to defend themselves, passing up the opportunity to retreat with the hope that they would be reinforced. Over the next hour, the Spanish were attacked from three sides thrice, and, while their commander was killed, they did not break. French cavalry annihilated the small Spanish force besieging the capital, and the rest of the Spanish army decided to surrender. However, some units were not informed about the surrender plans, and some Spanish troops fired on Conde. The French attacked the tercios for a fourth time, assisted by point-blank cannon fire, and every remaining Spanish soldier in three out of the five tercios was killed or surrendered, while the other two were allowed to retreat with their weapons out of respect. The battle shattered the myth of the tercio's invincibility and saved France from invasion.